With so many children taking these drugs, plenty of parents and doctors are concerned about potential side effects, including the possibility of curbed growth. Some studies have suggested that the drugs can cause growth to slow a bit, while others haven't found a link. Few studies have followed these kids beyond their youth to track their final heights. Now there's some reassuring news on that front: Research published online in Pediatrics on Monday found that children who took ADHD medicine didn't have height deficits in adulthood.

Researchers looked at medical records from people born in Rochester, Minn., from 1976 to 1982. They identified 340 children diagnosed with ADHD, and tracked them into adulthood. Each person's medical record was then compared with those of two other people, matched for age and gender but otherwise randomly selected, who didn't have ADHD. (All were participants in the Rochester Epidemiology Project, a long-term data collection and research collaboration.) The 171 children who took stimulants for ADHD started at an average of about 10 years of age, and took the drugs for about 4 1/2 years. (The study didn't look at newer, nonstimulant drugs like Strattera, which wasn't approved until 2002.)

Neither an ADHD diagnosis itself nor treatment with stimulant drugs was linked to a significant difference in growth or final height, compared to the average for that age and gender, says Dr. William Barbaresi, lead author of the study and a developmental-behavioral pediatrician at Boston Children's Hospital. The only significant effect was that, for boys treated with the drugs for at least three years, the medicines were associated with about a six-month delay in the peak growth spurt. But there was no significant effect on the ultimate height of those young men, says Barbaresi.

Still, it's crucial that doctors continue to monitor the growth of children taking these drugs, Barbaresi says. It's possible that some in the study were taken off their meds if their growth rate raised concerns. And because of where the research was conducted, the population was mostly white, which might also limit the findings.

But the research suggests that "in the real world, with clinicians making decisions, there's no long-term impact" on height, Barbaresi says. His study showed no relationship between dose or duration of treatment and adult height.

The research adds to the evidence suggesting that "this is not an issue that people have to worry about," says Stephen Faraone, a psychologist at SUNY Upstate Medical University who researches ADHD.

"It's a terrific study," says James Swanson, a pediatric psychologist at the University of California, Irvine who also studies ADHD. He's on a team looking into the effects of higher doses of stimulant drugs, taken over a longer period of time. Long-term data on growth from that study, he says, have not yet been published.